Hydrogen is a very common atom occurring in many fuels, often in the presence of carbon in organic compounds. Generally, hydrogen may be used for upgrading petroleum feed stock to more useful products. In addition, hydrogen is used in many chemical reactions, such as reducing or synthesizing compounds. Particularly, hydrogen is used as a primary chemical reactant in the production of useful commercial products, such as cyclohexane, ammonia, and methanol.
Hydrogen itself is quickly becoming a fuel of choice because it reduces green house emissions. Particularly, hydrogen can drive a fuel cell to produce electricity or can be used to produce a substantially clean source of electricity for powering industrial machines, automobiles, and other internal combustion-driven devices.
Hydrogen production systems include the recovery of bi-products from various industrial processes and the electrical decomposition of water. Presently the most economical means, however, is to remove the hydrogen from an existing organic compound. Several methods are known to remove or generate hydrogen from carbonaceous or hydrocarbon materials. Although many hydrocarbon molecules can be reformed to liberate hydrogen atoms, methane or natural gas is most commonly used.
Use of hydrocarbons as source materials has many inherent advantages. Hydrocarbon fuels are common enough to make production economical. Safe handling methods are well-developed to allow safe and expeditious transport of the hydrocarbons for use in the different reforming and generation techniques.
The main part of today's hydrogen production uses methane as a feedstock. Generally, steam methane reformers are used on the methane in large-scale industrial processes to liberate a stream of hydrogen. Steam methane reformers, however, generally produce less than 90% pure hydrogen molecules in their product streams. Along with the hydrogen streams, side products, such as carbon dioxide, methane, and other bi-products are also produced. The presence of the bi-products pollutes the hydrogen stream making it unusable without further purification.
The process of steam reformation of methane typically consists of reacting methane (from natural gas) with steam to produce CO and H2 (sometimes called synthesis gas). This reaction usually takes place over a nickel catalyst in a metal alloy tube at temperatures in the region of 800 to 1000 C and at pressures of 30 to 60 atmospheres. The reaction is equilibrium limited and is highly endothermic requiring heat input of 60 Kcal/mol CH4 including the heat needed to produce steam from liquid water. Heating the outside of the reactor chamber containing the reactants provides the heat for the reaction. The chemical reaction for the reacting of methane is:CH4+H2O=>CO+3 H2  (1) 
The CO is to be removed from the product stream for a suitably pure hydrogen stream. To accomplish this, the product gases require further reaction. The appropriate further reaction is shifting the product gases with steam (usually called the water gas reaction) to form additional hydrogen and CO. The CO is then removed from the gas mixture by a pressure swing absorption process to produce a clean stream of hydrogen. The shift reaction produces a second portion of hydrogen by the reaction of the carbon monoxide, from the reforming reaction, with steam.
The shift reaction consumes the carbon monoxide from the reforming reaction to produce carbon dioxide and additional hydrogen gas. Water injection cools the hot gases from the steam reformer by producing steam in a phase-shift, hence the name shift reaction. The steam reacts with the CO forming additional hydrogen and CO2. The reaction energy is substantially balanced so that little additional heat is required to keep the reaction going. The reaction produces a mixture of CO2 and hydrogen with small amounts of CO. The shift reaction is a costly unit of production, requiring significant equipment and operating costs. The chemical equation for the shift reaction is:CO+H2O=>CO2+H2  (2) 
Finally, a pressure swing adsorption process, i.e. bi-product removal in an absorption process, generally follows steam reformation and shift reaction. Pressure swing absorbers (PSAs) can generally reduce the bi-products formed leaving a hydrogen product of about 99% pure hydrogen. To effectively remove the bi-products from the hydrogen stream, PSAs must selectively absorb and hold the carbon dioxide.
Generally, in a PSA process, the hydrogen stream is passed over a filter or bed. The particular PSA composition is selected to optimize carbon dioxide absorption at the temperatures, pressures, and composition of the shift reaction. The inclusion of the PSA or reaction cooperator, for example a calcium constituent, in the PSA bed produces a substantially pure hydrogen product, but it also increases the hydrogen generation from the fuel. According to Le Chatelier's Principle, removing a product of a reaction will shift the equilibrium of the reaction, thereby increasing the production of the other reaction products.
The separation reaction consumes carbon dioxide from the shift reaction to produce the solid calcium carbonate product. Because all of the other reactants are gases, the calcium carbonate, being a solid, is substantially removed from the reaction. The rate of absorption slows as the free calcium volume declines. The chemical equation for the PSA reaction is as follows:CO2(g)+CaO(s)=CaCO3(s)  (3) 
As each of the PSA beds become filled or saturated with the absorbed carbon dioxide, transforming the calcium to calcium carbonate, the PSAs begin to exude carbon dioxide back into the hydrogen stream repolluting it. Mechanically, this can be done continuously by moving the carbonate to another section of the reactor for regeneration, or by intermittently taking the reactor off-line similar to commercially available Pressure Swing Adsorption (PSA) units. The calcium oxide is not consumed in the overall scheme, but provides an effective method of pushing (actually pulling) the formation of hydrogen to completion at a much lower temperature and a much higher purity than other techniques. Nonetheless, much unreacted carbon remains.
To prevent the repollution of the stream with exuded carbon dioxide, the stream is redirected to a different PSA bed. The saturated PSA bed is then unusable without some sort of regenerative process to liberate the bi-products. Regeneration has been a complex process requiring a great deal of heat to liberate the carbon dioxide, and even at high heat, the regeneration is generally incomplete, making the PSA less effective than in its initial absorption cycle. Therefore, there is an unmet need in the art for improved methods of PSA absorption and regeneration in isolating hydrogen from carbonaceous or hydrocarbon materials.